A young Kamen Rider fan is granted his wish of seeing Riders in person, initiating the ultimate Japanese superhero crossover meta film. The third and final installment of the Heisei Generations series finds Kamen Rider Zi-O and Kamen Rider Build joining forces with all of the other Heisei Generation Riders to reverse the damages of an evil Time Jacker named Tid, and save their legacy. Are Kamen Riders real? Will you believe?
After the end of the civil war that tore apart Japan, the new governors of Touto, Hokuto and Seito work together to reunify the country. However, they are actually members of an extraterrestrial race called the "Blood Tribe" (the same species as Evolto), who assumed their government positions as part of a plan to destroy Earth as they have done to Mars and other planets before. Considering Sento Kiryū (Kamen Rider Build) a major threat to their plans, the Blood Tribe manipulates his friends and other civilians into attacking him. With even his close ally Ryūga Banjō (Kamen Rider Cross-Z) now against him, Sento must fight to survive and stop the Blood Tribe's plan from succeeding.
Looking for something to do during the summer, Akihiko Suzuki teams up with four girls (Namie, Natsumi, Mishiyo, and Komugi) and a guy (Kosuke) to start a little cafe down by the beach. Actually, he is more interested in the girls than the job. They used to ignore him, but by working at the cafe, he hopes to start a friendship with them.
After the events of the previous film, the 17 years-old Sukeban Deka III, Yui Kazama, works for the Juvenile Security Bureau along with her older sisters Yuka and Yuma. This organization is led by politician Kuraudo Sekin, who fights juvenile crime in heavy-handed manners, to the extent to equip his student agents with triple-bladed yo-yo weapons. However, when Sekin's methods become too zealous, Yui quits the bureau and refuses to undertake undercover missions for them. It is soon discovered that Sekin's actual goal is to overthrow the Japanese government, and the Kazama sisters, along with a gang of young outcasts, have to stop him.
After the events of the TV series, the 18 year old Yoko Godai has abandoned her special agent Saki Asamiya name to return to her normal life, and is now studying for college entrance exams. However, she accidentally bumps into a young man named Kazuo Hagiwara trying to escape from a group of hitmen, and learns that he comes from Sanko Academy, a private school located in a remote island known as Hell's Castle. The school is ruled by a former revolutionary thought to be dead named Hattori who is trying to brainwash students into terrorists to help him stage a fascist coup d'etat in Japan.
